Re: [stella] Collaboration

Subject: Re: [stella] Collaboration
From: Thomas Jentzsch <tjentzsch@xxxxxx>
Date: Sat, 18 Jan 2003 14:36:10 +0100
Glenn wrote:
> I WAS counting on VDEL to make it so that the write to at least one of the
> sprites would not have to happen at a precise time.  Don't know if that's 
> really possible or not in this kernel, but that would help the tearing 
> issue because you'd be left with a matrix of 4 possible combinations for 
> the time-critical car and one of the missiles (both in left side, both in 
> right side, car in left and missile in right, missile in left and car in 
> right).

Today I finished the kernel where both missiles align to the tombstone
rows. So only one more to go, and I hope I can do that one without
splitting the kernels for X-positions.

> Ultimately I think some mid-screen kernel branching is going to be
> necessary because the bunching would need different kernels for
> alternating scanline pairs.

Yes, and branching costs precious time too.

> If you perform your branching during the grenade zones, then I can work the
> AI so that the two missiles will only cross if they are at least one 
> tombstone row apart, vertically.

I hope that won't be necessary.

> How big is it so far?

About 1.5K, but there is plenty of room for optimizations outside the

> I'm quite confident that the coarser movement will look okay.

Without trying?

> The sooner you find the magic solution to the tearing problem the
> sooner I can show the list a demo ;)

Well, in my general kernel (missiles differ by one scanline, P0_Y % 1 !=
P0_Y % 1) there is no tearing problem. Only the special two kernels 
where the missiles are on the same scanline (P0_Y % 1 = P0_Y % 1) are a
bit more complicated.

Have fun!
Thomas Jentzsch         | *** Every bit is sacred ! ***
tjentzsch at web dot de |

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